Planar gas discharge indicator

ABSTRACT

An alpha-numeric indicator of the planar gas tube variety wherein both the anode and cathode elements are planar surfaces supported in a common plane spacer from the supporting base of the assembly by electrical connections passing through the base.

United States Patent Warne 1 July 4, 1972 [54] PLANAR GAS DISCHARGE INDICATOR [72] Inventor: Leland C. Warne, Phoenix, Ariz.

[73] Assignee: Sperry Rand Corporation [22] Filed: Jan. 23, 1970 [21] Appl. No.: 5,435

[57.1 11.5.11. ......3l3/l09.5, 315/169, 340/336 [31! Int. (TL, ..Jllllj 7/42, 1101 k H60, 1105b 37/00 [51%| FieldofSearch ..340/336;313/109.5;315/169 [56] References Cited UNITED STATES PATENTS 3,553,603 l/1971 Leonard ..331/94 5 3,327,154 6/1967 Bowerman ..313/109 5 3,067,354 12/1962 Peterson 313/1095 X 3,260,880 7/1966 Kupsky ..313/109 5 3,517,245 6/1970 Dickson, Jr. et a1 ..3l3/l09.5 2,966,616 12/1960 Mash ..313/109.5 X 3,281,833 10/1966 Seidel ..313/109.5 UX

FOREIGN PATENTS OR APPLlCATlON S 39/11865 5/1964 Japan ..313/109.5 548,352 11/1957 Canada ..3 13/1095 Primary Examiner-Ronald L. Wibert Assistant ExaminerWarren A. Sklar Attorney-S. C. Yeaton 57 ABSTRACT An alpha-numeric indicator of the planar gas tube variety wherein both the anode and cathode elements are planar surfaces supported in a common plane spacer from the supporting base of the assembly by' electrical connections passing through the base.

6 Claims, 8 Drawing Figures P'A'TE'NTEDJuL 4:912

SHEET 10F 3 RE mm vm 0 w M E L FIG. I.

P'ATENIEDJ L I912 SHEET 2 [IF 3 INVENT ATTORNEY LELAND c. WARA/E 34A- J\ FIG. 40.

PATENTEDJUL 4 I972 I NVEN TOR.

LELAND C. WAR/V5 Mi ATTORNEY I PLANAR GAS DISCHARGE INDICATOR CROSS REFERENCES Ser. No. 742,662 now abandoned, filed July 5, 1968 and may be constructed in accordance with the method disclosed in Method for Manufacturing Planar Raised Cathode Gas Tubes, Ser. No. 5,436, the latter being filed concurrently with the instant application and both applications being assigned to the same assignee as the present invention.

DESCRIPTION OF THE PRIOR ART Previously, planar cathode element gas discharge tubes operated on the principle that one of the electrodes was in proximity with or a part of the transparent faceplate, usually the anode, and the other electrode was connected to the base, usually the cathode. The anode consisted of a uniform electrical coating, such as tin oxide, and commonly cooperating with each of the cathode elements. The cathode generally consisted of a plurality of cathode elements deposited on or attached to the base plate. Each cathode element wasconnected to a common electrical source but selectively activatable. The four parts of a gas tube (anode plate, cathode/base assembly, spacer and fill tube) are sealed together to form a hermetic envelope. The envelope is then evacuated, back filled with an ionizable gas such as neon, and sealed. To obtain the desired display information, dc power is applied between the anode and a predetennined array of cathode elements causing the gas about the cathode elements to ionize and visibly form the desired number or letter.

SUMMARY OF THE INVENTION The device of the instant invention is unique in concept in that both the anode and cathode elements are in essentially the same plane. In construction, the anode may horizontally surround as well as he in essentially the same plane as the cathode elements. Where the figure permits, such as the standard seven segment numeric, a separate anode piece may lie between and in essentially the same plane as the cathode elements. Each of these interior anode pieces are electrically connected to the surrounding anode.

The instant device may be conveniently, economically and accurately fabricated by the method disclosed in the copending patent application entitled Method for Manufacturing Planar Raised Cathode Gas Tubes, Ser. No. 5,436. As explained in that application, the cathode elements are delineated in a stencil-like fashion in a larger sheet and remain connected thereto by tabs. While still connected to the sheet, the elements are attached to the electrical connections extending from a base. After attachment, the cathode elements are severed from the sheet by a bum-off process in which the connecting tabs are melted by passing a current through them. An advantage of such method is the facile and accurate manner in which the cathode elements are aligned with each other and the electrical connections. The method is readily adaptable to the instant device in that both the anode and the cathode elements may be accurately positioned relative to one another and delineated in the sheet. Moreover, since the method involves attaching the elements to the electrical connections and segregating them from each other and the sheet from it will provide an accurate in-plane alignment of the elements.

The advantages of the planar raised cathode as discussed in patent application Ser. No. 742,662 (now abandoned) are preserved in the instant invention and are intended to be incorporated by reference in the instant application. Additional advantages are obtainable by the instant device and will be discussed in more detail below.

A primary object of the instant invention is to provide sharper character definition. I

Another object of the invention is to provide lower manufacturing cost for indicator gas tubes.

Another object of the invention is to provide longer life for indicator gas tubes.

Another object of the invention is to permit the manufacture of a plurality of individual anode/cathode assemblies or modules arranged in a display using a common module mounting base and gas envelope.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a three quarter exploded view of the components of the planar raised anode cathode gas tube of the present invention;

FIG. 2 is a modification of the configuration shown in FIG. 1 of the anode and cathode elements;

FIG. 3 illustrates a teaching of the invention wherein each numeral or character is in a self contained and replaceable module which may be of any exterior configuration;

FIGS. 4 and 4a are a representation of the cross section of a module such as in FIG. 3 taken along line 4-4.

FIG. 5 illustrates a modification of the individual or plural indicium indicators of FIGS. 1 and 3;

FIG. 6 illustrates a base subassembly having attached thereto the pins, anode and cathode elements; and

FIG. 7 illustrates a common gas envelop display for housing a plurality of completed base assemblies.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 illustrates an exploded view of the basic elements of an in-plane anode-cathode gas discharge indicator. The face plate 1 may be glass or any other transparent or translucent material which permits observation of the activated indicator element(s). Spacer 2 is designed to provide a chamber to contain an ionizable gas between the faceplate 1 and base 4. Alternatively, the base 4 may be manufactured with a peripheral ridge or wall which serves the same purpose as the spacer; or, the faceplate 1 may have a peripheral ridge or wall which, with the base 4, will provide the desired chamber. Either arrangement, if otherwise commercially feasible, permits deleting the spacer 2. FIGS. 4, 4a and 7 illustrate such an arrangement wherein the faceplate assembly is attached directly to the base assembly. These variations may be made for either the individual or multiple indicia gas tube assemblies and are to be considered as variations on the subsequently discussed embodiments. Fill tube 9 and hole 9 are located at any convenient point in the base 4 through which the chamber may be evacuated and filled with an ionizable gas. Alternatively, the fill tube 9 and hole 9' can be located in the spacer 2 or on faceplate 1 if the manufacturing requirements or the display panel within which the indicator is located so permits.

The anode and cathode elements are fabricated from an electrically conductive sheet by any number of well known processes such as stamping, etching, cutting by laser, u]- trasonic means, electroforming, or electrical discharge machining. Presently, satisfactory results in terms of cost and accuracy have been obtained by etching. Sheet 3 in the preferred embodiment is of stainless steel and approximately 0.005 inch thick and fabricated to obtain an outline of parts as shown. An additional advantage obtainable by these methods is that of precisely defining the anode cathode gap. As the gas tube indicator will not fire unless there exists a predetermined minimum firing potential dependent upon the gas pressure and the anode-cathode gap distance, the above-described method of partitioning the anode elements in respect to the cathode elements permits an accurate determination of the gap distance and the other two parameters can then be accurately forecast. Theaccurate determination of the gap also permits an increased control over the amount of shielding.

have sufficiently narrow cross section to provide a high resistance path to a current passed through it. The sheet is similar to a stencil in general configuration, however, instead of the desired figures being removed, the material representing intermittent channels forming the outline of the desired figures is removed. The orientation and size of the elements processed in sheet 3 may be of any configuration and depend only upon the nature of the characters desired. Sheet 3 may, in addition, contain other representations such as decimal point 6.

Referring still to FIG. 1, the glass base 4 contains a number of hermetically sealed electrical connecting pins 3', 3a, 5' and 6. In an alternate configuration (not shown) the pins may be replaced by any other electrically conducting support piece providing only that the attached anode and cathode elements are raised from the base. For example, the connection may be L" shaped, having the long leg lying on or imbedded in the base and extending beyond the edge of the base for attachment with driving circuitry; the short leg would extend perpendicularly from the base and have attached to it the anode or cathode segments. The long legs could, of course, be printed or otherwise deposited on the base 4.

In the illustrated configuration, the ends of the pins on the upper side of base 4 extend a predetermined distance; good results are obtained with a distance of about 0.005 inches. The pins extend below the base 4 bottom surface a convenient distance suitable for connection with a mating receptacle or other electrical attachment. A preferred method of assembling the base 4 and the pins 3', 3a, 5 and 6 assembly may be that of having the pins sealed in the base but with one end initially flush with the upper surface of base 4 and the other end extending therefrom. The side of the base having the flush pin terminations is then etched away so as to expose the desired length of each pin above the etched base surface. During etching, a cup-shaped indentation or moat 8 is formed in the base around the base of each pin. The moats formed during the base etching process result because the substrate-pin combination produces compressively strained seals; these strained glass seal areas etch more rapidly than the unstrained portions of the base. The advantage of the latter method is that of an increased operational life as a low resistance path between the pins formed by sputtered products is inhibited. Further details of the sputtered products effects are discussed in pending application entitled Planar Raised Cathode Alpha-Numeric Gas Discharge lndicator, Ser. No. 742,662, filed July 5,

The presently known best mode of joining the elements in sheet 1 to the pins is that of electrical welding. However, it is anticipated that other means for accomplishing the bond may be employed if circumstances indicate that another method is preferable. The fabricated sheet 3 is aligned by registration means (not shown) with the base 4 and the pin assembly so that each of the pins will contact its respective element. After alignment, a first electrode of a welder (not shown) is attached to a pin and a second electrode is placed on the associated segment in proximity to the pin under the element. Slight pressure is applied to the upper electrode to insure physical contact between the element and pin. Current of predetermined magnitude and duration flows between the electrodes causing the pin to become welded to the element. This process is repeated for each pin/segment combination, or may be accomplished in a single step with a multi-electrode welder.

To separate the elements from the sheet a method of dewelding is used. The tabs are of relatively small cross section and, as such, they constitute high resistance paths to an applied current. Any current passing through the tabs will cause a heat build up and if the current is large enough, the generated heat will melt the tabs. The burn-off process is accomplished by attaching a first electrode of a current source to an element and the second electrode is attached to sheet 3. A current will then flow from the first electrode through the element, through one or more of the tabs joining the element to sheet 3, and thence to the second electrode. The current will continue to flow until the heat build up in the tab or tabs is suflicient to melt the tab or tabs. When the tabs melt, the current path is open circuited indicating that the connection between the element and sheet 3 is severed.

At this point the anode elements 3 and 3a and the cathode elements 5 and 6 are individually attached to their respective pins 3', 3a, 5 6'; and the anode and cathode elements are mechanically and electrically severed from each other thereby forming a complete anode/cathode base subassembly.

The gas tube module can now be completed by attaching the spacer 2 and faceplate 1 to base 4 and sealing the assembly. The air in the chamber of the assembly is evacuated and then replaced, through fill tube 9 and hole 9, by a mixture of neon and argon or any other inert ionizable gas. A small amount of vaporized mercury may be included with the inert gas to prolong the life of the tube. Alternatively, the entire assembly may be sealed in a chamber containing the ionizable gas thus precluding the necessity for a fill-tube or filling operation as defined above. This latter described method may also be incorporated in the subsequently described gas tube modifications.

A modification of the configuration of a desired numeral, such as shown in FIG. 1, may be that of omitting the circumscribed anode elements (3a). In tests, the illumination of the cross element was reduced by approximately ten percent from that of the peripheral cathode elements.

FIG. 2 illustrates a further modification in constructing the illustrated numeral. Here, the anode 3 is comprised of a single piece and circumscribes each of the elements 5 and 6.

FIG. 3 illustrates a further modification of the basic invention. Previously, a plurality of numerals or characters were included within the gas tube assembly. In this embodiment, each character or numeral comprises an individual or separate gas tube module and each such module may be inserted in or when necessary exchanged with other modules in a common display panel having appropriate socket receiving means (not shown). The module may have any number of variations in terms of symbols or physical size, and the construction of these modules may be generally similar to that described in respect to FIG. 1.

FIG. 4 and FIG. 4a are illustrative of cross section variations of the gas tube assembly of FIGS. 1 and 2. The welds 7 caused by attaching the anode and cathode elements to their respective pins and the moat 8 formed during the etching of the base 4 are also shown. The gaseous envelope may be obtained by either incorporating a ridge in the base assembly or the faceplate and thereby obviate the necessity of a spacer.

FIG. 5 illustrates a further modification of the individual or multiple indicators. The base 4 has disposed or otherwise attached thereto pins 5' extending a uniform distance above the base. Cathode elements 5 are attached to these pin ends. The faceplate assembly 1 may comprise a faceplate having a ridge as shown or it may comprise a spacer and a flat faceplate as previously discussed. Around the periphery of base 4 there is disposed metallic siding 3b having a flange extending inwardly in essentially the same plane as the planar raised cathodes 5 and constitutes the anode element. The faceplate assembly 1 may be attached to the horizontal portion of the flange as shown or it may extend down to and embrace a portion of the siding. In operation, the display within which the aforedescribed module is mounted may have on the inside edge of the depression an electrical contact or other means to ensure a solid electrical connection with the anode element 3b. The display will also have appropriate means for mating the pins 5 to the driving circuitry to activate the desiredindicium. It is understood that the concept of the instant modification may be applied to either a rectangular, circular or other module base configurations.

FIG. 6 illustrates still further modifications of the construction of a plurality of gas tube indicators, and depicts a completed base assembly wherein the base 4 is circular. Such a circular base may have cost saving factors during the manufacturing process and may be considered a preferred embodiment for that reason. The base has disposed therein pins to which the elements 3 and 5 are bonded. The seven segment numeric shown is similar to that of FIG. 3 for a single character but it is understood that any other variation wherein the anode elements are substantially in the plane of the cathode elements may be incorporated without departing from the scope of the invention. In a preferred configuration, the symbol might extend beyond the circular base so as to provide the largest possible symbol for the smallest possible base diameter. In this way the symbols may be placed close together without having the manufacturing difliculties of producing rectangular bases and matching apertures 11 (FIG. 7) It is understood that the base assembly may also be rectangular or of any other desired configuration.

FIG. 7 illustrates a display 12 having disposed therein a plurality of apertures 11 of any desired configuration to receive the gas tube base assemblies of FIG. 6.

A plurality of base assemblies illustrated in FIG. 6 are selected and placed in and sealed to the predesigned apertures 1 l of display 12 and the unit is sealed as previously discussed. The electronic circuit is added. The display 12 may comprise a faceplate 1, a base member 4'and spacer 2 or the unit may be molded to incorporated the spacer 2 in either faceplate 1 or base member 4.

The operation of the completed display shown in FIG. 7 (base member with ridge and faceplate l) is similar to that of the previously discussed individual gas tube indicators but has certain commercial advantages. First, a display 12 of any size having any number of apertures may be fabricated. Secondly, the anode/cathode base assemblies may be mass produced for subsequent addition to a variety of displays. Thirdly, the use of a common gas envelope for a large number of indicium incurs the cost of filling and sealing only one envelope instead of filling and sealing each of the self contained modules. Fourthly, the unit may be assembled in a gaseous atmosphere precluding the step of evacuating the chamber and filling it with an ionizable gas and sealing it. I

The instant invention is a great improvement over the previously known gas tubes and obviates many of the difficulties found therein. The following is a summary of the more significant advances.

ln any gas tube there exists a problem of sputtered products collecting on the interior surfaces of the envelope, the rate of build up thereof on critical surfaces determining the life of the tube. The combination of the raised cathode and moat will alleviate this problem significantly. The positioning of the anode in substantially the same plane as the cathode, as in the instant invention, provides a physical barrier and tends to reduce the deposits on the base. It is also believed that the change from a vertical voltage potential gradient to a horizontal voltage potential gradient aids in reducing the sputter deposits at critical points in the envelope, primarily on the surface of the support base. However, this phenomenon has not yet been conclusively settled.

In the previous gas tube designs, the glow about the cathode elements was not sharply defined and tended to have a billowing-like edge. The instant invention produces a much more sharply defined edge as the glow does not extend beyond the adjacent anode elements. If desired, the configuration in FIG. 1 may be modified by deleting anodes 3a. This will cause some slight billowing about the inside edges of the cathodes 5. It may also cause the brightness of the center cathode element to be reduced by about ten percent in respect to the peripheral cathode elements.

While the anodes have been described in terms of being formedfrom the same sheet as the cathode, this is not to be construed as a limitation upon the inventive concept. Dependent upon the desired size and horizontal distance of the anode in respect to the cathode elements, it may be simply a wire or a plate lying in the general plane of the cathodes. If sharpness of the glow is paramount, the anode should be horizontally everywhere adjacent to but not in contact with the sides of the cathode elements. Where sharpness of the glow is not critical a remote anode element in the plane of the cathode elements may be used for a plurality of cathode element groups. Additional variations are contemplated and are to be construedas lying within the ambit of the instant inventive concept.

While the invention has been described in its preferred embodiment, it is to be understood that the words which have been used are words of description rather than limitation and that changes within the purview of the appended claims may be made without departing from the true scope and spirit of the invention in its broader aspects.

I claim:

l. A glow discharge type tube for displaying symbols or patterns comprising a closed hermetically sealed envelope having a substantially flat non-conductive back base and a light transmissive front viewing face,

an ionizable gas enclosed within said envelope,

a plurality of electrically conductive cathode supporting connector pins passing in hermetically sealed relation through the non-conductive back base into the interior of the hermetically sealed envelope and having portions exterior of the tube envelope for selective energization from a source of electrical excitation,

a plurality of relatively spaced fiat cathodes positioned to form a pattern and supported on ends of said pins interior of the envelope in a common plane spaced from and substantially parallel to the non-conductive back base, each cathode forming an elemental part of a desired pattern and the flat surface area thereof effectively shielding a portion of the interior surface of said non-conductive back base, and

flat planar anode means supported in said common plane and extending over a major portion of said plane to be cooperative with the cathodes for shielding the interior surface of the non-conductive back base, thereby inhibiting sputter deposition and the formation of cathode shorting paths along said base.

2. The apparatus of claim 1 wherein the cathodes are arranged in an alphanumeric symbol format and the anode means includes at least one member circumscribing the symbol format.

3. The apparatus of claim 2 wherein the anode means includes additional members each located within a region circumscribed by respective pluralities of cathodes.

4. The apparatus of claim 1 wherein the cathode to tube base spacing is on the order of 0.005 inches.

5. The apparatus of claim 1 wherein edges of the anode means are in close proximity to adjacent edges of the cathodes to restrict the extent of ionized glow about energized cathodes in a direction parallel to the non-collective back base and thereby sharply define the edge of the displayed symbols or patterns.

6. A glow discharge type tube for displaying symbols or patterns comprising a closed hermetically sealed envelope having a substantially flat non-conductive back base and a light transmissive front viewing face,

an ionizable gas enclosed within said envelope,

a plurality of electrically conductive cathode supporting connector pins passing in hermetically sealed relation through the non-conductive back base into the interior of the hermetically sealed envelope and having portions exterior of the tube envelope for selective energization from a source of electrical excitation,

a plurality of relatively spaced flat cathodes positioned to form a pattern and supported on ends of said pins interior of the envelope in a common plane spaced from and substantially parallel to the non-conductive back base, each cathode forming an elemental part of a desired pattern and the flat surface area thereof effectively shielding a portion of the interior surface of said non-conductive back base, and

flat planar anode means so constructed and arranged in said common plane that edges of the anode means are in close proximity to adjacent edges of the cathodes to restrict the extent of ionized glow about the energized cathodes in a direction parallel to the non-conductive back base and thereby sharply define the edge of the displayed symbols or patterns. 

1. A glow discharge type tube for displaying symbols or patterns comprising a closed hermetically sealed envelope having a substantially flat non-conductive back base and a light transmissive front viewing face, an ionizable gas enclosed within said envelope, a plurality of electrically conductive cathode supporting connector pins passing in hermetically sealed relation through the non-conductive back base into the interior of the hermetically sealed envelope and having portions exterior of the tube envelope for selective energization from a source of electrical excitation, a plurality of relatively spaced flat cathodes positioned to form a pattern and supported on ends of said pins interior of the envelope in a common plane spaced from and substantially parallel to the non-conductive back base, each cathode forming an elemental part of a desired pattern and the flat surface area thereof effectively shielding a portion of the interior surface of said non-conductive back base, and flat planar anode means supported in said common plane and extending over a major portion of said plane to be cooperative with the cathodes for shielding the interior surface of the non-conductive back base, thereby inhibiting sputter deposition and the formation of cAthode shorting paths along said base.
 2. The apparatus of claim 1 wherein the cathodes are arranged in an alphanumeric symbol format and the anode means includes at least one member circumscribing the symbol format.
 3. The apparatus of claim 2 wherein the anode means includes additional members each located within a region circumscribed by respective pluralities of cathodes.
 4. The apparatus of claim 1 wherein the cathode to tube base spacing is on the order of 0.005 inches.
 5. The apparatus of claim 1 wherein edges of the anode means are in close proximity to adjacent edges of the cathodes to restrict the extent of ionized glow about energized cathodes in a direction parallel to the non-collective back base and thereby sharply define the edge of the displayed symbols or patterns.
 6. A glow discharge type tube for displaying symbols or patterns comprising a closed hermetically sealed envelope having a substantially flat non-conductive back base and a light transmissive front viewing face, an ionizable gas enclosed within said envelope, a plurality of electrically conductive cathode supporting connector pins passing in hermetically sealed relation through the non-conductive back base into the interior of the hermetically sealed envelope and having portions exterior of the tube envelope for selective energization from a source of electrical excitation, a plurality of relatively spaced flat cathodes positioned to form a pattern and supported on ends of said pins interior of the envelope in a common plane spaced from and substantially parallel to the non-conductive back base, each cathode forming an elemental part of a desired pattern and the flat surface area thereof effectively shielding a portion of the interior surface of said non-conductive back base, and flat planar anode means so constructed and arranged in said common plane that edges of the anode means are in close proximity to adjacent edges of the cathodes to restrict the extent of ionized glow about the energized cathodes in a direction parallel to the non-conductive back base and thereby sharply define the edge of the displayed symbols or patterns. 